*{
    margin: 0px;
    padding: 0px;
}
ul li ul{
    display: none;
    left: -30px;
    top: 40px;
    list-style: none;

}
ul li ul li{
    height: 30px;
    width: 100%;
    line-height: 30px;
    text-align: center;
    border-style: solid;
    border-width: 1px;
    cursor: pointer;
    background-color: chocolate;
}
ul li ul li:hover{
    background-color:brown;
}
/* 大于号样式仅限于儿子 */
#menu>li{
    display: inline-block;
    width: 100%;
    height: 40px;
    border-style: solid;
    border-width: 1px;
    text-align: center;/* 左右居中 */
    line-height: 40px;/*行高与height一样 可以上下居中*/
    cursor: pointer;
    background-color:darkslategrey;
}
a{
    color: black;
}
a:hover{
    color: black;
}
body,div{
    padding: 0px;
    border: 0px;
    margin: 0px;
}
body{
    color: white;
    margin: 0px;
    height: 978px;
}
#header{
    height: 15%;

}
#top{
    height: 75%;
    background-image: url("/images/header.png");
}
#down{
    height: 25%;
    background-color: aliceblue;
}

#menudiv{
    width: 20%;
    height: 80%;
    background-color: lightblue;
    float: left;
}
#function{
    width: 80%;
    height: 80%;
    float: right;
}
